Conventional diesel engines include, in the exhaust passage, a diesel particulate filter (DPF), which captures particulates contained in exhaust, and an exhaust purifying device, which includes an oxidation catalyst. Such an exhaust purifying device treats exhaust to raise the temperature in order to maintain the function of purifying exhaust. The treatment regenerates the DPF by burning the particulates captured by the DPF and activates the oxidation catalyst.
For example, Patent Document 1 discloses a combustor arranged upstream of a DPF and an oxidation catalyst. Exhaust gas with the temperature raised by the combustor is sent to the DPF and the oxidation catalyst, so that the DPF is regenerated and the oxidation catalyst is activated. The combustor includes a premixing chamber, in which fuel gas and exhaust are mixed to generate a pre-mixed air-fuel mixture. The pre-mixed air-fuel mixture is sent to an ignition device (not shown).